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(11) | EP 0 749 165 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Thin film transistor in insulated semiconductor substrate and manufacturing method thereof |
| (57) It is an object to obtain a semiconductor device with the LDD structure having both
operational stability and high speed and a manufacturing method thereof. A high concentration
region (11) with boron of about 1×1018/cm3 introduced therein is formed extending from under a channel formation region (4)
to under a drain region (6) and a source region (6') in a silicon substrate (1). The
high concentration region (11) is formed in the surface of the silicon substrate (1)
under the channel formation region (4), and is formed at a predetermined depth from
the surface of the silicon substrate (1) under the drain region (6) and the source
region (6'). A low concentration region (10) is formed in the surface of the silicon
substrate (1) under the drain region (6) and the source region (6'). The formation
of the high concentration region only in the surface of the semiconductor substrate
under the channel formation region surely suppresses an increase in the leakage current
and an increase in the drain capacitance. |